The present invention relates to a vacuum cleaner comprising a drive motor and a suction fan in which the suction air flow is guided via a suction socket into a receptacle, which is closed by a cover containing the drive motor and the suction fan, and wherein the suction fan sucks air out of the receptacle.
Such a commercial vacuum cleaner is known from German Offenlegungsschrift 23 51 769 and has an angular suction socket radially extending from the receptacle and opening axially into the receptacle containing a dust filter. The dust filter is designed to retain dirt that is transported within the suction air flow. The suction opening of the suction fan that generates the suction air stream is arranged above the dust filter in the cover and sucks the air out of the receptacle. Due to the arrangement of the suction socket a main flow from the suction socket through the filter to the suction opening of the suction fan results. Besides this main flow an auxiliary flow with substantially reduced flow velocities is also formed. In areas protected by the filter bag extremely flow-reduced areas are present.
The dirt particles within the main flow hit with high kinetic energy the filter wall and can even partially penetrate the filter wall. Thus, the filtering effect can be substantially reduced so that the outblowing air stream is greatly laden with dirt. Furthermore, since essentially only the directly accessible areas of the filter are used and after their saturation the filter effect is diminished, a filter bag must be exchanged prematurely even though parts of the filter lying in the flow-protected areas are still effective.
In order to provide for a uniform flow through the filter, it has been suggested in U.S. Pat. No. 3,286,446 and French patent 623,781 to suck the suction air flow via a comb-shaped suction head from the receptacle, whereby the walls of the suction head are provided with a plurality of inlet flow openings. The arrangement of the suction socket is such that the entering suction air stream flows without any further deflection into the suction head, so that dirt particles hit the filter at high kinetic energies and can damage the filter.
It is therefore an object of the present invention to provide a vacuum cleaner of the aforementioned kind with which a uniform usage of the dust-retaining filter with a minimal pollution of the exit air is ensured.